The present invention relates generally to diagnostic imaging and, more particularly, to a CT detector with an integrated air gap. More particularly, the CT detector includes a scintillator array having an anti-reflective layer is attached to a photodiode array having a textured surface such that a controlled air gap exists therebetween.
Typically, in computed tomography (CT) imaging systems, an x-ray source emits a fan-shaped beam toward a subject or object, such as a patient or a piece of luggage. Hereinafter, the terms “subject” and “object” shall include anything capable of being imaged. The beam, after being attenuated by the subject, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is typically dependent upon the attenuation of the x-ray beam by the subject. Each detector element of the detector array produces a separate electrical signal indicative of the attenuated beam received by each detector element. The electrical signals are transmitted to a data processing system for analysis which ultimately produces an image.
Generally, the x-ray source and the detector array are rotated about the gantry within an imaging plane and around the subject. X-ray sources typically include x-ray tubes, which emit the x-ray beam at a focal point. X-ray detectors typically include a collimator for collimating x-ray beams received at the detector, a scintillator for converting x-rays to light energy adjacent the collimator, and photodiodes for receiving the light energy from the adjacent scintillator and producing electrical signals therefrom.
Typically, each scintillator of a scintillator array converts x-rays to light energy. Each scintillator discharges light energy to a photodiode adjacent thereto. Each photodiode detects the light energy and generates a corresponding electrical signal. The outputs of the photodiodes are then transmitted to the data processing system for image reconstruction.
Known CT detectors utilize a contiguous layer of epoxy to optically couple the photodiode array to the scintillator array. This layer of epoxy is generally referred as an “opti-coupler”. The opti-coupler must be of sufficient adhesion strength to maintain a consistent bond between the photodiode array and scintillator array along both the width and length of the arrays. That is, the opti coupler must be formed of a composite that is able to withstand the stress induced in the scintillator and photodiode arrays that result when materials with similar thermal coefficients of expansion are coupled to one another.
Advancements have been made in opti-coupler design and fabrication to withstand the stress associated with coupling materials with different thermal expansion characteristics to one another. Despite these advancements, known opti-couplers remain susceptible to cracking or breaking away from the scintillator and/or photodiode array. This premature cracking or breaking away can result in catastrophic failure of the CT detector thereby warranting full detector replacement and downtime of the CT system.
Therefore, it would be desirable to design a CT detector wherein the photodiode array and scintillator array are coupled to one another absent a contiguous optical coupling epoxy layer.